// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2014 Benoit Steiner <benoit.steiner.goog@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_CXX11_TENSOR_TENSOR_FUNCTORS_H
#define EIGEN_CXX11_TENSOR_TENSOR_FUNCTORS_H

namespace Eigen {
namespace internal {

/** \internal
 * \brief Template functor to compute the modulo between an array and a scalar.
 */
template<typename Scalar>
struct scalar_mod_op
{
	EIGEN_DEVICE_FUNC scalar_mod_op(const Scalar& divisor)
		: m_divisor(divisor)
	{
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar operator()(const Scalar& a) const { return a % m_divisor; }
	const Scalar m_divisor;
};
template<typename Scalar>
struct functor_traits<scalar_mod_op<Scalar>>
{
	enum
	{
		Cost = scalar_div_cost<Scalar, false>::value,
		PacketAccess = false
	};
};

/** \internal
 * \brief Template functor to compute the modulo between 2 arrays.
 */
template<typename Scalar>
struct scalar_mod2_op
{
	EIGEN_EMPTY_STRUCT_CTOR(scalar_mod2_op)
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar operator()(const Scalar& a, const Scalar& b) const { return a % b; }
};
template<typename Scalar>
struct functor_traits<scalar_mod2_op<Scalar>>
{
	enum
	{
		Cost = scalar_div_cost<Scalar, false>::value,
		PacketAccess = false
	};
};

template<typename Scalar>
struct scalar_fmod_op
{
	EIGEN_EMPTY_STRUCT_CTOR(scalar_fmod_op)
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Scalar operator()(const Scalar& a, const Scalar& b) const
	{
		return numext::fmod(a, b);
	}
};
template<typename Scalar>
struct functor_traits<scalar_fmod_op<Scalar>>
{
	enum
	{
		Cost = 13, // Reciprocal throughput of FPREM on Haswell.
		PacketAccess = false
	};
};

template<typename Reducer, typename Device>
struct reducer_traits
{
	enum
	{
		Cost = 1,
		PacketAccess = false,
		IsStateful = false,
		IsExactlyAssociative = true
	};
};

// Standard reduction functors
template<typename T>
struct SumReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T t, T* accum) const
	{
		internal::scalar_sum_op<T> sum_op;
		*accum = sum_op(*accum, t);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reducePacket(const Packet& p, Packet* accum) const
	{
		(*accum) = padd<Packet>(*accum, p);
	}

	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		internal::scalar_cast_op<int, T> conv;
		return conv(0);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet initializePacket() const
	{
		return pset1<Packet>(initialize());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T accum) const { return accum; }
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet finalizePacket(const Packet& vaccum) const
	{
		return vaccum;
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalizeBoth(const T saccum, const Packet& vaccum) const
	{
		internal::scalar_sum_op<T> sum_op;
		return sum_op(saccum, predux(vaccum));
	}
};

template<typename T, typename Device>
struct reducer_traits<SumReducer<T>, Device>
{
	enum
	{
		Cost = NumTraits<T>::AddCost,
		PacketAccess = PacketType<T, Device>::HasAdd,
		IsStateful = false,
		IsExactlyAssociative = NumTraits<T>::IsInteger
	};
};

template<typename T>
struct MeanReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE MeanReducer()
		: scalarCount_(0)
		, packetCount_(0)
	{
	}

	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T t, T* accum)
	{
		internal::scalar_sum_op<T> sum_op;
		*accum = sum_op(*accum, t);
		scalarCount_++;
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reducePacket(const Packet& p, Packet* accum)
	{
		(*accum) = padd<Packet>(*accum, p);
		packetCount_++;
	}

	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		internal::scalar_cast_op<int, T> conv;
		return conv(0);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet initializePacket() const
	{
		return pset1<Packet>(initialize());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T accum) const
	{
		internal::scalar_quotient_op<T> quotient_op;
		return quotient_op(accum, T(scalarCount_));
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet finalizePacket(const Packet& vaccum) const
	{
		return pdiv(vaccum, pset1<Packet>(T(packetCount_)));
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalizeBoth(const T saccum, const Packet& vaccum) const
	{
		internal::scalar_sum_op<T> sum_op;
		internal::scalar_quotient_op<T> quotient_op;
		return quotient_op(sum_op(saccum, predux(vaccum)),
						   T(scalarCount_ + packetCount_ * unpacket_traits<Packet>::size));
	}

  protected:
	DenseIndex scalarCount_;
	DenseIndex packetCount_;
};

template<typename T, typename Device>
struct reducer_traits<MeanReducer<T>, Device>
{
	enum
	{
		Cost = NumTraits<T>::AddCost,
		PacketAccess = PacketType<T, Device>::HasAdd && PacketType<T, Device>::HasDiv && !NumTraits<T>::IsInteger,
		IsStateful = true,
		IsExactlyAssociative = NumTraits<T>::IsInteger
	};
};

template<typename T, bool IsMax = true, bool IsInteger = true>
struct MinMaxBottomValue
{
	EIGEN_DEVICE_FUNC static EIGEN_STRONG_INLINE T bottom_value() { return Eigen::NumTraits<T>::lowest(); }
};
template<typename T>
struct MinMaxBottomValue<T, true, false>
{
	EIGEN_DEVICE_FUNC static EIGEN_STRONG_INLINE T bottom_value() { return -Eigen::NumTraits<T>::infinity(); }
};
template<typename T>
struct MinMaxBottomValue<T, false, true>
{
	EIGEN_DEVICE_FUNC static EIGEN_STRONG_INLINE T bottom_value() { return Eigen::NumTraits<T>::highest(); }
};
template<typename T>
struct MinMaxBottomValue<T, false, false>
{
	EIGEN_DEVICE_FUNC static EIGEN_STRONG_INLINE T bottom_value() { return Eigen::NumTraits<T>::infinity(); }
};

template<typename T, int NaNPropagation = PropagateFast>
struct MaxReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T t, T* accum) const
	{
		scalar_max_op<T, T, NaNPropagation> op;
		*accum = op(t, *accum);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reducePacket(const Packet& p, Packet* accum) const
	{
		scalar_max_op<T, T, NaNPropagation> op;
		(*accum) = op.packetOp(*accum, p);
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		return MinMaxBottomValue<T, /*IsMax=*/true, Eigen::NumTraits<T>::IsInteger>::bottom_value();
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet initializePacket() const
	{
		return pset1<Packet>(initialize());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T accum) const { return accum; }
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet finalizePacket(const Packet& vaccum) const
	{
		return vaccum;
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalizeBoth(const T saccum, const Packet& vaccum) const
	{
		scalar_max_op<T, T, NaNPropagation> op;
		return op(saccum, op.predux(vaccum));
	}
};

template<typename T, typename Device, int NaNPropagation>
struct reducer_traits<MaxReducer<T, NaNPropagation>, Device>
{
	enum
	{
		Cost = NumTraits<T>::AddCost,
		PacketAccess = PacketType<T, Device>::HasMax,
		IsStateful = false,
		IsExactlyAssociative = (NaNPropagation != PropagateFast)
	};
};

template<typename T, int NaNPropagation = PropagateFast>
struct MinReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T t, T* accum) const
	{
		scalar_min_op<T, T, NaNPropagation> op;
		*accum = op(t, *accum);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reducePacket(const Packet& p, Packet* accum) const
	{
		scalar_min_op<T, T, NaNPropagation> op;
		(*accum) = op.packetOp(*accum, p);
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		return MinMaxBottomValue<T, /*IsMax=*/false, Eigen::NumTraits<T>::IsInteger>::bottom_value();
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet initializePacket() const
	{
		return pset1<Packet>(initialize());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T accum) const { return accum; }
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet finalizePacket(const Packet& vaccum) const
	{
		return vaccum;
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalizeBoth(const T saccum, const Packet& vaccum) const
	{
		scalar_min_op<T, T, NaNPropagation> op;
		return op(saccum, op.predux(vaccum));
	}
};

template<typename T, typename Device, int NaNPropagation>
struct reducer_traits<MinReducer<T, NaNPropagation>, Device>
{
	enum
	{
		Cost = NumTraits<T>::AddCost,
		PacketAccess = PacketType<T, Device>::HasMin,
		IsStateful = false,
		IsExactlyAssociative = (NaNPropagation != PropagateFast)
	};
};

template<typename T>
struct ProdReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T t, T* accum) const
	{
		internal::scalar_product_op<T> prod_op;
		(*accum) = prod_op(*accum, t);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reducePacket(const Packet& p, Packet* accum) const
	{
		(*accum) = pmul<Packet>(*accum, p);
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		internal::scalar_cast_op<int, T> conv;
		return conv(1);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet initializePacket() const
	{
		return pset1<Packet>(initialize());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T accum) const { return accum; }
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE Packet finalizePacket(const Packet& vaccum) const
	{
		return vaccum;
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalizeBoth(const T saccum, const Packet& vaccum) const
	{
		internal::scalar_product_op<T> prod_op;
		return prod_op(saccum, predux_mul(vaccum));
	}
};

template<typename T, typename Device>
struct reducer_traits<ProdReducer<T>, Device>
{
	enum
	{
		Cost = NumTraits<T>::MulCost,
		PacketAccess = PacketType<T, Device>::HasMul,
		IsStateful = false,
		IsExactlyAssociative = true
	};
};

struct AndReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(bool t, bool* accum) const { *accum = *accum && t; }
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool initialize() const { return true; }
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool finalize(bool accum) const { return accum; }
};

template<typename Device>
struct reducer_traits<AndReducer, Device>
{
	enum
	{
		Cost = 1,
		PacketAccess = false,
		IsStateful = false,
		IsExactlyAssociative = true
	};
};

struct OrReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(bool t, bool* accum) const { *accum = *accum || t; }
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool initialize() const { return false; }
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE bool finalize(bool accum) const { return accum; }
};

template<typename Device>
struct reducer_traits<OrReducer, Device>
{
	enum
	{
		Cost = 1,
		PacketAccess = false,
		IsStateful = false,
		IsExactlyAssociative = true
	};
};

// Argmin/Argmax reducers.  Returns the first occurrence if multiple locations
// contain the same min/max value.
template<typename T>
struct ArgMaxTupleReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T t, T* accum) const
	{
		if (t.second < accum->second) {
			return;
		} else if (t.second > accum->second || accum->first > t.first) {
			*accum = t;
		}
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		return T(0, NumTraits<typename T::second_type>::lowest());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T& accum) const { return accum; }
};

template<typename T, typename Device>
struct reducer_traits<ArgMaxTupleReducer<T>, Device>
{
	enum
	{
		Cost = NumTraits<T>::AddCost,
		PacketAccess = false,
		IsStateful = false,
		IsExactlyAssociative = true
	};
};

template<typename T>
struct ArgMinTupleReducer
{
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE void reduce(const T& t, T* accum) const
	{
		if (t.second > accum->second) {
			return;
		} else if (t.second < accum->second || accum->first > t.first) {
			*accum = t;
		}
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T initialize() const
	{
		return T(0, NumTraits<typename T::second_type>::highest());
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE T finalize(const T& accum) const { return accum; }
};

template<typename T, typename Device>
struct reducer_traits<ArgMinTupleReducer<T>, Device>
{
	enum
	{
		Cost = NumTraits<T>::AddCost,
		PacketAccess = false,
		IsStateful = false,
		IsExactlyAssociative = true
	};
};

template<typename T, typename Index, size_t NumDims>
class GaussianGenerator
{
  public:
	static const bool PacketAccess = false;

	EIGEN_DEVICE_FUNC GaussianGenerator(const array<T, NumDims>& means, const array<T, NumDims>& std_devs)
		: m_means(means)
	{
		EIGEN_UNROLL_LOOP
		for (size_t i = 0; i < NumDims; ++i) {
			m_two_sigmas[i] = std_devs[i] * std_devs[i] * 2;
		}
	}

	EIGEN_DEVICE_FUNC T operator()(const array<Index, NumDims>& coordinates) const
	{
		T tmp = T(0);
		EIGEN_UNROLL_LOOP
		for (size_t i = 0; i < NumDims; ++i) {
			T offset = coordinates[i] - m_means[i];
			tmp += offset * offset / m_two_sigmas[i];
		}
		return numext::exp(-tmp);
	}

  private:
	array<T, NumDims> m_means;
	array<T, NumDims> m_two_sigmas;
};

template<typename T, typename Index, size_t NumDims>
struct functor_traits<GaussianGenerator<T, Index, NumDims>>
{
	enum
	{
		Cost = NumDims * (2 * NumTraits<T>::AddCost + NumTraits<T>::MulCost +
						  functor_traits<scalar_quotient_op<T, T>>::Cost) +
			   functor_traits<scalar_exp_op<T>>::Cost,
		PacketAccess = GaussianGenerator<T, Index, NumDims>::PacketAccess
	};
};

template<typename Scalar>
struct scalar_clamp_op
{
	EIGEN_DEVICE_FUNC inline scalar_clamp_op(const Scalar& _min, const Scalar& _max)
		: m_min(_min)
		, m_max(_max)
	{
	}
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Scalar operator()(const Scalar& x) const
	{
		return numext::mini(numext::maxi(x, m_min), m_max);
	}
	template<typename Packet>
	EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE const Packet packetOp(const Packet& x) const
	{
		return internal::pmin(internal::pmax(x, pset1<Packet>(m_min)), pset1<Packet>(m_max));
	}
	const Scalar m_min;
	const Scalar m_max;
};
template<typename Scalar>
struct functor_traits<scalar_clamp_op<Scalar>>
{
	enum
	{
		Cost = 2 * NumTraits<Scalar>::AddCost,
		PacketAccess = (packet_traits<Scalar>::HasMin && packet_traits<Scalar>::HasMax)
	};
};

} // end namespace internal
} // end namespace Eigen

#endif // EIGEN_CXX11_TENSOR_TENSOR_FUNCTORS_H
